There are four common types of water heater used in residential construction; each has their pros and cons of course, but what does the 2022 Energy Code think of hot water?
Water Heater Overview
Tank gas water heater: Common and affordable but takes up space, not very efficient, has a low recovery rate.
Heat pump water heater (HPWH): Electric and efficient but takes up considerable space and has a low recovery rate. These are becoming more cost competitive every day but still often seen as a pricier option.
Tankless gas water heater: Affordable, minimal space required, energy efficient depending on the make/model, and has an ‘infinite’ supply of hot water.
Tankless electric water heater: Cheapest initial cost option, an ‘infinite’ supply of hot water, and minimal space required, but is very inefficient, so comes with high utility bills with regular use.
There is also a Tank Electric Resistance water heater, but those are so inefficient as to be generally phasing out.
If Choosing Gas, Plan for Electric Ready
A consideration when deciding the type of water heater for your project is that all new construction and additions (if a water heater is installed in the added floor area) are required to meet the Electric Ready requirements when installing a gas water heater:
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- A dedicated 125-volt (V) electrical receptacle that is within 3 feet of the water heater and accessible to the water heater with no obstructions, and be connected to a three conductor, 10 AWG branch circuit. In addition, the unused conductor must be labeled and electrically isolated and have a reserved circuit breaker space.
- A condensate drain that is no more than 2 inches higher than the base of the installed water heater and allows natural draining without pump assistance
Energy Code Requirements
For a new single-family residence, the 2022 Prescriptive requirements are either.
- a 240 volt HPWH with stipulations for tank location (see section 150.1(c)8) or,
- a 240 volt HPWH that is NEEA* Tier 3 or higher, or
- a solar water heating system with electric backup and a minimum solar savings fraction of 0.70.
* NEEA = Northwest Energy Efficiency Alliance
The exceptions for the Prescriptive Method of compliance are significant, especially #1 and #2.
Exception 1: In climate zones 3, 4, 13, and 14, a gas instantaneous water heater with an input of 200,000btuh or less and no storage tank may be installed.
Exception 2: An instantaneous electric water heater with Point of Use distribution (RA4.4.5) may be installed for new dwelling units with a Conditioned Floor Area of 500 SF or less.
Exception 3: A 120v HPWH may be installed for new dwelling units with 1 bedroom or less.
As we know, the Prescriptive requirements are what we are compared against (the baseline) when we use the Performance method. This means without a project being applicable to one of the prescriptive Exceptions, it will be compared against a 240V NEEA Tier 3 HPWH. This does not eliminate the use of systems other than HPWHs; it just requires that you utilize the Performance Method for all climate zones other than 3, 4, 13, and 14.
Water heater efficiency is regulated by Title 20 which aligns with the Federal Efficiency standards. This means that Title 24 does not dictate the minimum required efficiency of your water heaters, but units with an efficiency beyond the Federal Minimum can help with compliance, when included in the Performance method.
Distribution Systems – Recirculation takes a hit
Part of hot water system compliance is the distribution throughout the home, for example, the pipe insulation, length of pipe, and Recirculation systems. The best summary and understanding of how Title 24 handles Distribution compliance is Table 5-9 in the Compliance Manual.
Table 5-9: Applicability of Distribution Systems Options Within a Dwelling Unit
| Distribution System Types | Distribution System Types | System Serving a Single Dwelling Unit |
| No HERS Inspection Required Trunk and Branch – Standard (STD) | 1.0 | Yes |
| No HERS Inspection Required Compact Design – Basic (CHWDS) | 0.7 | Yes |
| No HERS Inspection Required Parallel Piping (PP) | 1.1 | Yes |
| No HERS Inspection Required Point of Use (POU) | 0.3 | Yes |
| No HERS Inspection Required Recirculation: Non-Demand Control Options (R-ND) | 9.8 | Yes |
| No HERS Inspection Required Recirculation with Manual Demand Control (R-Dman) | 1.75 | Yes |
| No HERS Inspection Required Recirculation with Motion Sensor Demand Control (R-DAuto) | 2.6 | Yes |
| HERS Inspection Required Pipe Insulation (PIC-H) | 0.85 | Yes |
| HERS Inspection Required Parallel Piping with 5’ maximum length (PP-H) | 1 | Yes |
| HERS Inspection Required Compact Design – Expanded (CHWDS-H) | 0.3 – 0.71 | Yes |
| HERS Inspection Required Recirculation with Manual Demand Control (R-Drmc-H) | 1.6 | Yes |
| HERS Inspection Required Recirculation with Motion Sensor Demand Control (RDRsc-H) | 2.4 | Yes |
1. The multiplier for the Compact Design – Expanded credit varies depending on the home’s floorplan and water heater location. See Section 5.6.2.4 for more information.
The Assigned Distribution System Multiplier column is the Credit (<1) or Penalty (>1) associated with the Distribution type and associated HERS measures.
It’s worth noting that a Non-Demand Controlled Recirculation gives the largest penalty of x9.8 and the smallest penalty is x1.6 for a HERS Inspected Manual Demand Control Recirculation system. This means that any Recirculation system will give a penalty that needs to be offset as part of the Performance method.
The largest credit available to distribution systems is the Point of Use design or HERS inspected Compact Design x0.3, both of which require the proximity of the water heater to be close to the end use fixtures.
Conclusion
California continues to move toward building electrification by setting electric heat pump water heaters as the prescriptive baseline in most cases. However, there are several exceptions to be considered, as well as a detailed look at hot water distribution, to make sure that the best system is selected, and code compliance is achieved.
For more about this topic or other Energy Code/Title 24 compliance questions, contact a 3C-REN Energy Code Coach.
